I love NaNo. I do my best in it every year. And it's like I always tell other writers that are considering joining: it's not a matter of whether or not you can finish. It's all about getting your mind working and getting yourself to start writing. It's about working toward a goal and testing your own limits as a writer. So what if you don't reach the goal? What does that mean? That you should try harder next time...that you should perfect your skills a bit more. Personally, I embrace every opportunity presented to me to help improve my prowess as a writer, and I think you all should, as well.
I reached my NaNo goal two years in a row, my second and third. This past year, however, I didn't do so great. But remember, everyone: there will be people participating in JulNoWriMo this year. Don't forget to get involved in that one. <3